The report, which is based primarily on measurements from the comScore Media Metrix Multi-Platform and comScore Mobile Metrix, highlights the key trends that shaped the 2015 media landscape, including the growth in social media and smartphone use. Mobile apps—driven largely by smartphones, which now make up 79 percent of the mobile phone market— were found to be the most popular way to consume social media sites such as Facebook, Snapchat, and Instagram.

When it comes to the platform with the widest appeal, the clear winner is Facebook, which leads social networks in both audience size and engagement. In fact, more than 90 percent of American adults devote two full workdays a month (15 to 18 hours) to the social network, Quartz reports. The platform accounts for one in every six minutes spent online, and more than one in every five minutes spent on mobile devices.

Though Snapchat follows Facebook in terms of highest engagement per visitor, its user base (in terms of age) is much less diverse. Almost half of its users are between 18 and 24 (more than 3 in 5 in this age group use the app every month), and two-thirds are between 18 and 24. Only 8 percent of adults ages 35+ use the app.